Radio link failure (RLF) happens in a mobile communication network when a mobile station, e.g. a mobile telephone, loses connection with the communication network in an uncontrolled manner. Radio link failures usually do not occur randomly. Typically, radio link failures occur at certain locations, or when a mobile station is moving out of the network coverage area of cell and into the network coverage area of another cell that has not been configured correctly. A reason for a connection loss may for example be that the mobile station is rapidly leaving the radio coverage area of the base station which is serving the mobile station. In such a situation, if RLF cannot be avoided, it is desired that the mobile station as soon as possible reconnects to the communication network in order to minimize the interruption time, a loss of transmission data and the perceived service degradation for the user of the mobile station For this purpose, after losing connection with the communication network, the mobile station performs a plurality of network reconnection procedures including selecting a new base station and cell and accessing the new base station in order to reconnect to the communication network.
For next generation mobile networks (NGMN) according to the Long Term Evolution (LTE) of the 3GPP (Third Generation Partnership Project) radio technology, it is proposed that a user equipment (UE) which detects that it is effected by a RLF, shall move to the LTE_IDLE state and perform a service request in order to reconnect to the network and recover the radio network bearers. The LTE_IDLE state in LTE is a power conversation state for the UE. In this state, the UE is not transmitting or receiving data packets to or from the network. In LTE_IDLE state, no context about the UE is stored in the evolved Node B (eNodeB), i.e. in the base station which is serving the UE. Therefore, the eNodeB has no information regarding the UE which is requesting to reconnect available.
In order to reconnect the UE to the communication network, it is necessary that the evolved packet core (EPC) of the communication network is involved in the reconnection process, i.e. context information regarding the UE has to be obtained by the eNodeB via the EPC. EPC is the mobile packet backbone network behind the eNodeBs. A state transition from LTE_IDLE state to LTE_IDLE active state, i.e. the state in which the UE is registered with the communication network and a Radio Resource Control (RRC) connection with the eNodeB is established, will take approximately 100 ms. Hence, such a network reconnection after RLF may take a long time and may occupy core network elements which are needed for other network tasks.
Document EP 1 720 367 A1 concerns a method of operating a user equipment. If a problem, such as loss of coverage or call has occurred, information about the location where the problem has occurred is stored in the memory of the user equipment. After successful recovery from the problem, an alternative base station is also stored in the memory. Next time the same problem is encountered at the same location, the user equipment uses the previous information for alleviating the problem or performing a fast recovery.